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Entomology and Plant Pathology, Oklahoma State University
127 Noble Research Center, Stillwater, OK74078
405.744.5527
Vol. 12, No. 1
http://entoplp.okstate.edu/Pddl/
Jan 25, 2013
Alfalfa Weevil Egg Populations 2013
Phil Mulder and Kelly Seuhs,
Extension Entomologist and OSU Extension Associate
Alfalfa weevil egg populations for January are located in the attached table. In addition, degree days through January 24, 2013 are presented in the last column. For the purpose of comparison, January egg populations and viability of those eggs for the previous collection years are also depicted in the table. Viability measurements for this year’s samples have been processed; with four locations (Grady, Tillman, Major and Alfalfa Counties) having sufficient egg numbers for testing. An average of 68 % viability was obtained. Compared to previous sample years (2004-2007, 2012), relatively low numbers of eggs were recovered. However, there is a slight increase in comparison to this time last year. In 2013, degree days through January 24 are averaging 51.2 across the ten sample sites.
In an ongoing effort to identity effects on alfalfa weevil and aphid populations over the current and previous years, we continue to look at the percentage of normal precipitation in each of the ten counties sampled this year. From the fall of 2010 through most of 2011, a large portion of the state was in an exceptional drought. As much as two thirds of the state did not receive any measurable rainfall until late summer or early fall of 2011 and the cycle continued in 2012.Currently, even with the moisture received last fall and thus far this year, most of the state is still in an extreme drought with well below average rainfall. While those deficits may not totally account for the numbers of alfalfa weevil eggs recovered this year, if you look at the impact from the extreme temperatures the last two summers (50+ days over 100 degrees), the combination of persistent drought with extremely high temperatures during the summer months of 2011, may have resulted in increased mortality of summer aestivating (inactive in summer) adult weevils.

Entomology and Plant Pathology, Oklahoma State University
127 Noble Research Center, Stillwater, OK74078
405.744.5527
Vol. 12, No. 1
http://entoplp.okstate.edu/Pddl/
Jan 25, 2013
Alfalfa Weevil Egg Populations 2013
Phil Mulder and Kelly Seuhs,
Extension Entomologist and OSU Extension Associate
Alfalfa weevil egg populations for January are located in the attached table. In addition, degree days through January 24, 2013 are presented in the last column. For the purpose of comparison, January egg populations and viability of those eggs for the previous collection years are also depicted in the table. Viability measurements for this year’s samples have been processed; with four locations (Grady, Tillman, Major and Alfalfa Counties) having sufficient egg numbers for testing. An average of 68 % viability was obtained. Compared to previous sample years (2004-2007, 2012), relatively low numbers of eggs were recovered. However, there is a slight increase in comparison to this time last year. In 2013, degree days through January 24 are averaging 51.2 across the ten sample sites.
In an ongoing effort to identity effects on alfalfa weevil and aphid populations over the current and previous years, we continue to look at the percentage of normal precipitation in each of the ten counties sampled this year. From the fall of 2010 through most of 2011, a large portion of the state was in an exceptional drought. As much as two thirds of the state did not receive any measurable rainfall until late summer or early fall of 2011 and the cycle continued in 2012.Currently, even with the moisture received last fall and thus far this year, most of the state is still in an extreme drought with well below average rainfall. While those deficits may not totally account for the numbers of alfalfa weevil eggs recovered this year, if you look at the impact from the extreme temperatures the last two summers (50+ days over 100 degrees), the combination of persistent drought with extremely high temperatures during the summer months of 2011, may have resulted in increased mortality of summer aestivating (inactive in summer) adult weevils.